Heretofore, a light emission apparatus 100 having a configuration shown in FIG. 45 has been proposed (JP 2008-91831A: Patent Document 1). The light emission apparatus 100 includes a submount substrate 120 having a nitride-based ceramic substrate 121, an Au layer 124 provided on a surface of the nitride based ceramic substrate 121, an oxide layer 123 interposed between the nitride based ceramic substrate 121 and the Au layer 124, and an LED light-emitting element 126 mounted on the submount substrate 120 via a solder layer 125. The oxide layer 123 includes a metal oxide as a main component. The submount substrate 120 has a reflecting layer 122 composed of at least one of Ag and Al that is formed on the surface of the nitride-based ceramic substrate 121 so as not to overlap the Au layer 124.
Patent Document 1 discloses that, for the purpose of extracting light efficiently from the LED light-emitting element 126, it is preferable to use the nitride-based ceramic substrate 121 of aluminum nitride having high reflectance.
Also, heretofore, a chip-type light-emitting element having a configuration shown in FIG. 46 has been proposed (JP 11-112025A: Patent Document 2). The chip-type light-emitting element includes an insulating substrate 201, an LED chip 206 that is mounted on a surface of the insulating substrate 201, and a package 207 which covers the LED chip 206 and surroundings thereof.
Patent Document 2 discloses that blue light propagating toward the back face of the substrate of the LED chip 206 can be reflected by the insulating substrate 201 that is a white insulating substrate composed of ceramics such as alumina and aluminum nitride.
Also, heretofore, as shown in FIG. 47, a configuration has been proposed in which a light emission apparatus is mounted on an external circuit substrate 301 (JP 2006-237557A: Patent Document 3). The light emission apparatus includes: a light-emitting element housing package having a substrate 304 and a reflecting member 302; and a light-emitting element 306 constituted by an LED chip mounted on a mounting portion 304a of the substrate 304.
Patent Document 3 discloses that the substrate 304 and the reflecting member 302 are preferably composed of white ceramics. Also, Patent Document 3 discloses a lighting apparatus including the above-mentioned light emission apparatus as a light source.
In the light emission apparatus 100 having the configuration shown in FIG. 45, it is speculated that part of light emitted from a light-emitting layer of the LED light-emitting element 126 propagates toward the nitride-based ceramic substrate 121 through the LED light-emitting element 126 and is reflected by the solder layer 125. However, in the light emission apparatus 100, it is speculated that light outcoupling efficiency decreases due to absorption, multiple reflection and the like of the light reflected by the solder layer 125 in the LED light-emitting element 126.
In the chip-type light-emitting element having the configuration shown in FIG. 46, blue light that propagates toward the back face of the substrate of the LED chip 206 is reflected by the insulating substrate 201. It is speculated that light outcoupling efficiency decreases due to absorption, multiple reflection and the like of the light in the LED chip 206.
In the configuration shown in FIG. 47, part of the light emitted from a light-emitting layer of the light-emitting element 306 propagates toward the substrate 304 through the light-emitting element 306, and is reflected by the substrate 304. It is speculated that light outcoupling efficiency decreases due to absorption, multiple reflection, and the like of the light in the light-emitting element 306.